1. Field of the Invention
The invention relates to a display apparatus and an optical device, and more particularly to a display apparatus and a liquid crystal lens.
2. Description of Related Art
According to the main principle of stereo display techniques, the left eye and the right eye of a viewer respectively receive different images, and the images received by the left eye and the right eye of the viewer are analyzed and are overlapped by the brain, such that the viewer perceives gradation and depth information of the images and thereby generates stereo vision. Accordingly, in order to display stereo images on a flat display, two sets of images information alternatively need to be provided in the same image frame to simulate vision of two eyes. The two sets of images information are then respectively received by two eyes of the viewer through a particular optical device, so as to achieve stereo display effects.
At present, two auto-stereoscopic techniques are applied to accomplish the stereo display effects with naked eyes, i.e., either a parallax barrier or a column lens array may be utilized to project images to a viewer's left and right eyes, respectively. In addition, a liquid crystal lens stereo display has been proposed to replace the stereo display with the design of parallax barrier or column lens array, so as to form a switchable display capable of displaying two-dimensional (2D) images or three-dimensional (3D) images. In the liquid crystal lens stereo display, liquid crystal molecules in the liquid crystal layer are driven by the electric field applied thereto, such that the direction of the major axis of the liquid crystal molecules is changed along with variations in the electric field intensity. As such, the refractive index distribution of the liquid crystal lens in the stereo display may be similar to that of a physical lens. Nonetheless, the liquid crystal lens requires a complicated electrode design and a complex driving way for equalizing the function of the liquid crystal lens to the function of the physical lens. Hence, the electric field distribution and the design of the liquid crystal lens may be further improved.